1. Field of the Invention
The present invention relates to a polymer-modified resin comprising a hydroxy-functional and/or carboxy-functional polyester with dicidol in the alcohol component and a glycidyl-containing, optionally hydroxy-functional or carboxyl-containing polyacrylate.
2. Description of the Related Art
Different polymers are normally miscible with one another only with great difficulty if at all, since the Gibbs's mixing enthalpy of polymers is generally positive. This is one reason why polyesters are often immiscible and incompatible with polyacrylates. By the polymerization of acrylic monomers into a polyester matrix, however, it is possible to prepare stable mixtures.
EP 0 184 761 describes a low molecular mass liquid reaction product of a hydroxyl-containing polyacrylate prepared in a polyester polyol. A disadvantage of such products is the low molecular weight and the associated unsatisfactory adhesion to substrates. EP 206 072 describes a semicontinuous process for preparing the abovementioned products at a temperature of at least 150° C.
EP 0 896 991 describes an acrylic copolymer in which the fraction of the copolymer, which is composed of a polyester, is below 10%. The polyester described possesses OH numbers of between 50 and 350 mg KOH/g and acid numbers of between 1 and 50 mg KOH/g.
EP 0 607 792 discloses water-dilutable polyester-polyacrylate polymers in which the polyacrylate is prepared free-radically from its monomers in the presence of the polyester. The polyesters used are likewise of relatively low molecular mass, since the OH numbers are between 100 and 600 mg KOH/g and the acid numbers are between 0 and 15 mg KOH/g.
As experience has shown, the low molecular weight, owing to the relatively high OH numbers and acid numbers of such polyesters, leads to poor adhesion properties on substrates and also to poorer mechanical properties such as flexibility, for example.
EP 0 541 604 (WO 92/02590) discloses coating compositions based on hydroxyl-containing binders formed from polyesters and polyacrylates, the polyacrylates being prepared at least partly in the polyester and there being isocyanate crosslinkers present.
In accordance with the same preparation principle, EP 0 776 920 (DE 195 44 737) describes special polyester-acrylate-based binders.
None of these patents uses dicidol-containing polyesters.